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       # ABIT COMPUTER CORPORATION
       
          AH4
       
          Processor    80486SX/80486DX/CX486DX2/80486DX2                 
          Processor    20/25/33/40/50(internal)/66(internal)MHz          
          Speed        
          Chip Set     SIS                                               
          Max. Onboard 128MB                                             
          DRAM         
          Cache        128/256/512KB                                     
          BIOS         Award                                             
          Dimensions   330mm x 218mm                                     
          I/O Options  32-bit VESA local bus slots (2), green PC         
                       connector                                         
          NPU Options  None                                              
       
   IMG IMG 1
          
       
          +------------------------------------------------------------+
          |                        CONNECTIONS                         |
          |------------------------------------------------------------|
          | Purpose           | Location  | Purpose         | Location |
          |-------------------+-----------+-----------------+----------|
          | External battery  |    J1     | Reset switch    |   JW3    |
          |-------------------+-----------+-----------------+----------|
          | Green PC          |   JP45    | Turbo LED       |   JW4    |
          | connector         | (pins 7 - |                 |          |
          |                   |    8)     |                 |          |
          |-------------------+-----------+-----------------+----------|
          | Power LED &       |    JW1    | Turbo switch    |   JW5    |
          | keylock           |           |                 |          |
          |-------------------+-----------+-----------------+----------|
          | Speaker           |    JW2    | 32-bit VESA     |  SL1 -   |
          |                   |           | local bus slots |   SL3    |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |                 USER CONFIGURABLE SETTINGS                 |
          |------------------------------------------------------------|
          |               Function               | Jumper |  Position  |
          |--------------------------------------+--------+------------|
          | » | Factory configured - do not      |   J2   |    Open    |
          |   | alter                            |        |            |
          |---+----------------------------------+--------+------------|
          | » | CMOS memory normal operation     |  JP16  | pins 1 & 2 |
          |   |                                  |        |   closed   |
          |---+----------------------------------+--------+------------|
          |   | CMOS memory clear                |  JP16  | pins 2 & 3 |
          |   |                                  |        |   closed   |
          |---+----------------------------------+--------+------------|
          | » | Monitor type select color        |  JP17  |   Closed   |
          |---+----------------------------------+--------+------------|
          |   | Monitor type select monochrome   |  JP17  |    Open    |
          |---+----------------------------------+--------+------------|
          | » | Factory configured - do not      |  JP19  |    Open    |
          |   | alter                            |        |            |
          |---+----------------------------------+--------+------------|
          | » | Factory configured - do not      |  JP26  |    Open    |
          |   | alter                            |        |            |
          |---+----------------------------------+--------+------------|
          | » | Factory configured - do not      |  JP30  |    Open    |
          |   | alter                            |        |            |
          |---+----------------------------------+--------+------------|
          | » | Factory configured - do not      |  JP31  |    Open    |
          |   | alter                            |        |            |
          |---+----------------------------------+--------+------------|
          | » | Factory configured - do not      |  JP42  |    Open    |
          |   | alter                            |        |            |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |                     DRAM CONFIGURATION                     |
          |------------------------------------------------------------|
          | Size |    Bank 0     |   Bank 1    |   Bank 2   |  Bank 3  |
          |------+---------------+-------------+------------+----------|
          | 1MB  | (1) 256K x 36 |    NONE     |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 2MB  | (1) 256K x 36 | (1) 256K x  |    NONE    |   NONE   |
          |      |               |     36      |            |          |
          |------+---------------+-------------+------------+----------|
          | 2MB  | (1) 512K x 36 |    NONE     |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 4MB  | (1) 512K x 36 | (1) 512K x  |    NONE    |   NONE   |
          |      |               |     36      |            |          |
          |------+---------------+-------------+------------+----------|
          | 4MB  |  (1) 1M x 36  |    NONE     |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 4MB  | (1) 256K x 36 | (1) 256K x  | (1) 512K x |   NONE   |
          |      |               |     36      |     36     |          |
          |------+---------------+-------------+------------+----------|
          | 5MB  | (1) 256K x 36 | (1) 1M x 36 |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 6MB  | (1) 256K x 36 | (1) 256K x  |  (1) 1M x  |   NONE   |
          |      |               |     36      |     36     |          |
          |------+---------------+-------------+------------+----------|
          | 6MB  | (1) 512K x 36 | (1) 1M x 36 |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 8MB  | (1) 256K x 36 | (1) 256K x  | (1) 512K x | (1) 1M x |
          |      |               |     36      |     36     |    36    |
          |------+---------------+-------------+------------+----------|
          | 8MB  | (1) 512K x 36 | (1) 512K x  |  (1) 1M x  |   NONE   |
          |      |               |     36      |     36     |          |
          |------+---------------+-------------+------------+----------|
          | 8MB  |  (1) 1M x 36  | (1) 1M x 36 |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 8MB  |  (1) 2M x 36  |    NONE     |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 10MB | (1) 256K x 36 | (1) 256K x  |  (1) 1M x  | (1) 1M x |
          |      |               |     36      |     36     |    36    |
          |------+---------------+-------------+------------+----------|
          | 12MB | (1) 512K x 36 | (1) 512K x  |  (1) 1M x  | (1) 1M x |
          |      |               |     36      |     36     |    36    |
          |------+---------------+-------------+------------+----------|
          | 12MB |  (1) 1M x 36  | (1) 1M x 36 |  (1) 1M x  |   NONE   |
          |      |               |             |     36     |          |
          |------+---------------+-------------+------------+----------|
          | 16MB |  (1) 2M x 36  | (1) 2M x 36 |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 16MB |  (1) 1M x 36  | (1) 1M x 36 |  (1) 1M x  | (1) 1M x |
          |      |               |             |     36     |    36    |
          |------+---------------+-------------+------------+----------|
          | 16MB |  (1) 4M x 36  |    NONE     |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 17MB | (1) 256K x 36 | (1) 4M x 36 |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 18MB | (1) 256K x 36 | (1) 256K x  |  (1) 4M x  |   NONE   |
          |      |               |     36      |     36     |          |
          |------+---------------+-------------+------------+----------|
          | 20MB | (1) 512K x 36 | (1) 512K x  |  (1) 4M x  |   NONE   |
          |      |               |     36      |     36     |          |
          |------+---------------+-------------+------------+----------|
          | 20MB |  (1) 1M x 36  | (1) 4M x 36 |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 24MB |  (1) 2M x 36  | (1) 2M x 36 |  (1) 2M x  |   NONE   |
          |      |               |             |     36     |          |
          |------+---------------+-------------+------------+----------|
          | 24MB | (1) 512K x 36 | (1) 512K x  |  (1) 1M x  | (1) 4M x |
          |      |               |     36      |     36     |    36    |
          |------+---------------+-------------+------------+----------|
          | 24MB |  (1) 1M x 36  | (1) 1M x 36 |  (1) 4M x  |   NONE   |
          |      |               |             |     36     |          |
          |------+---------------+-------------+------------+----------|
          | 32MB |  (1) 2M x 36  | (1) 2M x 36 |  (1) 2M x  | (1) 2M x |
          |      |               |             |     36     |    36    |
          |------+---------------+-------------+------------+----------|
          | 32MB |  (1) 4M x 36  | (1) 4M x 36 |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 32MB |  (1) 8M x 36  |    NONE     |    NONE    |   NONE   |
          |------+---------------+-------------+------------+----------|
          | 36MB | (1) 512K x 36 | (1) 512K x  |  (1) 4M x  | (1) 4M x |
          |      |               |     36      |     36     |    36    |
          |------+---------------+-------------+------------+----------|
          | 36MB |  (1) 1M x 36  | (1) 4M x 36 |  (1) 4M x  |   NONE   |
          |      |               |             |     36     |          |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |                 DRAM CONFIGURATION (CON’T)                 |
          |------------------------------------------------------------|
          | Size  |   Bank 0    |   Bank 1   |   Bank 2   |   Bank 3   |
          |-------+-------------+------------+------------+------------|
          | 36MB  | (1) 1M x 36 |  (1) 8M x  |    NONE    |    NONE    |
          |       |             |     36     |            |            |
          |-------+-------------+------------+------------+------------|
          | 40MB  | (1) 1M x 36 |  (1) 1M x  |  (1) 4M x  |  (1) 4M x  |
          |       |             |     36     |     36     |     36     |
          |-------+-------------+------------+------------+------------|
          | 40MB  | (1) 1M x 36 |  (1) 1M x  |  (1) 8M x  |    NONE    |
          |       |             |     36     |     36     |            |
          |-------+-------------+------------+------------+------------|
          | 48MB  | (1) 4M x 36 |  (1) 4M x  |  (1) 4M x  |    NONE    |
          |       |             |     36     |     36     |            |
          |-------+-------------+------------+------------+------------|
          | 48MB  | (1) 4M x 36 |  (1) 8M x  |    NONE    |    NONE    |
          |       |             |     36     |            |            |
          |-------+-------------+------------+------------+------------|
          | 64MB  | (1) 4M x 36 |  (1) 4M x  |  (1) 4M x  |  (1) 4M x  |
          |       |             |     36     |     36     |     36     |
          |-------+-------------+------------+------------+------------|
          | 64MB  |  (1) 16M x  |    NONE    |    NONE    |    NONE    |
          |       |     36      |            |            |            |
          |-------+-------------+------------+------------+------------|
          | 64MB  | (1) 4M x 36 |  (1) 4M x  |  (1) 8M x  |    NONE    |
          |       |             |     36     |     36     |            |
          |-------+-------------+------------+------------+------------|
          | 64MB  | (1) 8M x 36 |  (1) 8M x  |    NONE    |    NONE    |
          |       |             |     36     |            |            |
          |-------+-------------+------------+------------+------------|
          | 65MB  | (1) 256K x  | (1) 16M x  |    NONE    |    NONE    |
          |       |     36      |     36     |            |            |
          |-------+-------------+------------+------------+------------|
          | 68MB  | (1) 1M x 36 | (1) 16M x  |    NONE    |    NONE    |
          |       |             |     36     |            |            |
          |-------+-------------+------------+------------+------------|
          | 68MB  | (1) 1M x 36 |  (1) 8M x  |  (1) 8M x  |    NONE    |
          |       |             |     36     |     36     |            |
          |-------+-------------+------------+------------+------------|
          | 72MB  | (1) 1M x 36 |  (1) 1M x  | (1) 16M x  |    NONE    |
          |       |             |     36     |     36     |            |
          |-------+-------------+------------+------------+------------|
          | 72MB  | (1) 1M x 36 |  (1) 1M x  |  (1) 8M x  |  (1) 8M x  |
          |       |             |     36     |     36     |     36     |
          |-------+-------------+------------+------------+------------|
          | 80MB  | (1) 4M x 36 | (1) 16M x  |    NONE    |    NONE    |
          |       |             |     36     |            |            |
          |-------+-------------+------------+------------+------------|
          | 80MB  | (1) 4M x 36 |  (1) 8M x  |  (1) 8M x  |    NONE    |
          |       |             |     36     |     36     |            |
          |-------+-------------+------------+------------+------------|
          | 96MB  | (1) 4M x 36 |  (1) 4M x  | (1) 16M x  |    NONE    |
          |       |             |     36     |     36     |            |
          |-------+-------------+------------+------------+------------|
          | 96MB  | (1) 4M x 36 |  (1) 4M x  |  (1) 8M x  |  (1) 8M x  |
          |       |             |     36     |     36     |     36     |
          |-------+-------------+------------+------------+------------|
          | 96MB  | (1) 8M x 36 |  (1) 8M x  |  (1) 8M x  |    NONE    |
          |       |             |     36     |     36     |            |
          |-------+-------------+------------+------------+------------|
          | 128MB |  (1) 16M x  | (1) 16M x  |    NONE    |    NONE    |
          |       |     36      |     36     |            |            |
          |-------+-------------+------------+------------+------------|
          | 128MB | (1) 8M x 36 |  (1) 8M x  |  (1) 8M x  |  (1) 8M x  |
          |       |             |     36     |     36     |     36     |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |                    CACHE CONFIGURATION                     |
          |------------------------------------------------------------|
          |    Size    |    Bank 0     |    Bank 1     |      TAG      |
          |------------+---------------+---------------+---------------|
          |   128KB    |  (4) 32K x 8  |     NONE      |  (1) 8K x 8   |
          |------------+---------------+---------------+---------------|
          |   256KB    |  (4) 32K x 8  |  (4) 32K x 8  |  (1) 32K x 8  |
          |------------+---------------+---------------+---------------|
          |   256KB    |  (4) 64K x 8  |     NONE      |  (1) 32K x 8  |
          |------------+---------------+---------------+---------------|
          |   512KB    |  (4) 64K x 8  |  (4) 64K x 8  |  (1) 32K x 8  |
          |------------+---------------+---------------+---------------|
          |   512KB    | (4) 128K x 8  |     NONE      |  (1) 32K x 8  |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |                 CACHE JUMPER CONFIGURATION                 |
          |------------------------------------------------------------|
          |   Size   |   JP1    |   JP2    |   JP4   |  JP40  |  JP41  |
          |----------+----------+----------+---------+--------+--------|
          |  128KB   |  1 & 2   |  1 & 2   |  1 & 2  | 1 & 2  | 1 & 2  |
          |----------+----------+----------+---------+--------+--------|
          |  256KB   |  2 & 3   |  2 & 3   |  1 & 2  | 2 & 3  | 2 & 3  |
          |----------+----------+----------+---------+--------+--------|
          |  256KB   |  1 & 2   |  2 & 3   |  1 & 2  | 1 & 2  | 1 & 2  |
          |----------+----------+----------+---------+--------+--------|
          |  512KB   |  2 & 3   |  2 & 3   |  2 & 3  | 2 & 3  | 2 & 3  |
          |----------+----------+----------+---------+--------+--------|
          |  512KB   |  1 & 2   |  2 & 3   |  2 & 3  | 1 & 2  | 1 & 2  |
          |------------------------------------------------------------|
          | Note: Pins designated should be in the closed position.    |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |                   CPU TYPE CONFIGURATION                   |
          |------------------------------------------------------------|
          |   Type   |  JP8  |  JP9   | JP11  | JP12  |  JP14  | JP15  |
          |----------+-------+--------+-------+-------+--------+-------|
          | 80486SX  | 2 & 3 |  Open  | Open  | 3 & 4 | 2 & 3  | 4 & 5 |
          |----------+-------+--------+-------+-------+--------+-------|
          | CX486DX  | 1 & 2 | Closed | 2 & 3 | 2 & 3 | 1 & 2, | 2 & 3 |
          |          |       |        |       |       | 3 & 4  |       |
          |----------+-------+--------+-------+-------+--------+-------|
          | 80486DX  | 1 & 2 | Closed | 2 & 3 | 3 & 4 | 2 & 3  | 4 & 5 |
          |----------+-------+--------+-------+-------+--------+-------|
          | 80486DX2 | 1 & 2 | Closed | 2 & 3 | 3 & 4 | 2 & 3  | 4 & 5 |
          |------------------------------------------------------------|
          | Note: Pins designated should be in the closed position.    |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |               CPU TYPE CONFIGURATION (CON’T)               |
          |------------------------------------------------------------|
          |    Type    |  JP21   |  JP22   |  JP24   |  JP25  |  JP46  |
          |------------+---------+---------+---------+--------+--------|
          |  80486SX   |  2 & 3  |  1 & 2  |  Open   |  Open  | 2 & 3  |
          |------------+---------+---------+---------+--------+--------|
          |  CX486DX   |  1 & 2  |  2 & 3  |  2 & 3  | 2 & 3  | 1 & 2  |
          |------------+---------+---------+---------+--------+--------|
          |  80486DX   |  2 & 3  |  1 & 2  |  Open   |  Open  | 2 & 3  |
          |------------+---------+---------+---------+--------+--------|
          |  80486DX2  |  2 & 3  |  1 & 2  |  Open   |  Open  | 2 & 3  |
          |------------------------------------------------------------|
          | Note: Pins designated should be in the closed position.    |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |                  CPU SPEED CONFIGURATION                   |
          |------------------------------------------------------------|
          |  Speed   |   JP5   |   JP6   |   JP7   |       JP20        |
          |----------+---------+---------+---------+-------------------|
          |  20MHz   | Closed  |  Open   | Closed  | pins 1 & 2 closed |
          |----------+---------+---------+---------+-------------------|
          |  25MHz   | Closed  | Closed  |  Open   | pins 1 & 2 closed |
          |----------+---------+---------+---------+-------------------|
          |  33MHz   |  Open   | Closed  | Closed  | pins 1 & 2 closed |
          |----------+---------+---------+---------+-------------------|
          |  40MHz   | Closed  |  Open   |  Open   | pins 2 & 3 closed |
          |----------+---------+---------+---------+-------------------|
          |  50iMHz  | Closed  | Closed  |  Open   | pins 1 & 2 closed |
          |----------+---------+---------+---------+-------------------|
          |  66iMHz  |  Open   | Closed  | Closed  | pins 1 & 2 closed |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |                   BUS SPEEDCONFIGURATION                   |
          |------------------------------------------------------------|
          |         CPU speed          |             JP29              |
          |----------------------------+-------------------------------|
          |          <=33MHz           |       pins 1 & 2 closed       |
          |----------------------------+-------------------------------|
          |           >33MHz           |       pins 2 & 3 closed       |
          +------------------------------------------------------------+
       
          +------------------------------------------------------------+
          |               VESA WAIT STATE CONFIGURATION                |
          |------------------------------------------------------------|
          |        Wait states         |             JP28              |
          |----------------------------+-------------------------------|
          |       0 wait states        |       pins 1 & 2 closed       |
          |----------------------------+-------------------------------|
          |        1 wait state        |       pins 2 & 3 closed       |
          +------------------------------------------------------------+